GC-MS Autotune

[CTSchemlab]

We have an unusual situation going on with our Agilent 7890 / 5975C GC-MS system. Here is the problem...

For the past year when we do the autotune everything passes and comes out great but when we go to run our calibration standards it fails for linearity, 0.995. Now it just doesn't fail that once it will continute to fail for 3 days. Then miraculously on day 4 the calibration passes achieving a 0.998/0.999 and the instrument is stable for a few weeks. After those few weeks go by the response drops and we have to retune the instrument. And again 3-4 days go by where the responses for calibration are all over the place and we can not achieve linearity but on day 3 or 4 we are good to go.

The analytes being injected on this system is for phthalates - plasticizers.

This is what we have tried:
1. Called Agilent and have had them here numerous times. They are still trying to fix this.
2. The entire inlet has been swapped out with a new S/S one.
3. Prepared new calibration standards
4. Performed Leak checks
5. Cleaned the source many many times
6. Changed the type of inlet liner and septa.
7. We have tried hundreds of injections with the Agilent FID (n- tetra, penta, hexa decane in Hexane) standard and method (to rule out wether or not it may be our standards and method) and the response increases 30% from the initial injection directly after tuning in a 24 hour period.
8. Also there was a PM recently performed
After all of this the problem is still there.

Has anyone else out there ever seen this happen?
PLEASE HELP!

[WK]

Hi,
Have you at any time had good chromatography from the GC-MS when running other samples/methods/test mixes?
Is it a problem just when analysing phthalates?
WK

[JTM]

Can you post a tune? Is there a reason you need an Autotune rather than a Standard spectra tune?

Maybe we could take a look at the tune values and see if anything is out of order?

[JI2002]

A couple of comments:

Linearity has nothing to do with what tune file is being used in the run method.

You can't change your tune file on a daily basis if you want your ICAL to last long.

In our lab our ICAL last from 6 month to more than 1 year which was unheared of to our auditor. We only adjust the tune manually when needed rather than running a new autotune.(we never use autotune).